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12 comments
Associate

Join Date: Aug 2007
Location: Canada
Posts: 48

Relay-Based Multivibrator

10/06/2009 10:12 AM

Hello All,

Again I'm working on some ancient piece of equipment, relay based automation.

Almost no documentation. Local maintenance team so far concentrated of shotgun approach, but they run out of things to shoot at and called me.

There is a bi-stable multivibrator based circuit (at the heart of the problem) build on contactors sic! (some with delay). Although I'm pretty ancient (graduated in 1974), I cannot recall a design like that.

I will have to do some reverse engineering to figure it out, tried some searches but come up empty-handed, may be some of you out there are old (read: experienced) enough to give me a hint?

Thanks

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Guru
India - Member - New Member Engineering Fields - Electromechanical Engineering - New Member

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#1

Re: relay based multivibrator..

10/06/2009 12:54 PM

This can work, but not sure if this is what you are looking.cap can be used to change frequency.

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Guru
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#2
In reply to #1

Re: relay based multivibrator..

10/06/2009 1:18 PM

better one with diode.

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Power-User

Join Date: Dec 2006
Posts: 252
Good Answers: 4
#3

Re: Relay Based Multivibrator..

10/06/2009 3:58 PM

kaztronics; sound like a forward/reverse set up for motor/s? they are interlocked with normally closed switches, & held in place with normally open switches, only one can closed at a time, the time delay may allow the motor to stop/slow down before reversing it. perry

Associate

Join Date: Aug 2007
Location: Canada
Posts: 48
#4
In reply to #3

Re: Relay Based Multivibrator..

10/06/2009 4:44 PM

you're close Perry, they drive hydrolic system that moves the table on the grinder.

Have to figure out how they're activated. I see there is another delay relay, switching on/off as limit switch is activated.

Thanks for the input guys.

Kaz

Guru
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#11
In reply to #4

Re: Relay Based Multivibrator..

10/09/2009 7:36 AM

Regards.

<< they drive hydrolic system that moves the table on the grinder >>

Limit switches on both ends are used in such cases as:

Up-Down or left-right movements. In case of heavy loads if Micro-switches are used operate a relay to switch the load.

<< Have to figure out how they're activated >>

One way is as you pointed out; another delay relay but the end-limit swich is a change over switch which cuts the circuit of previous movment & connects the reverse movement circuit.

Relays may perform multi-jobs as they may have more poles or 2 or more CO-MP switches can be used.

Relays are preferred because in case of failure of switch will produce a complicated fault while failure of a relay will give a clear fault.

Have a fine day !!!!!

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Guru
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#5

Re: Relay-Based Multivibrator

10/07/2009 4:15 AM

I may be poking my nose in here unwanted, apologies if true.....but:-

Do you need to use this relay system for reasons of cost or historical value?

Because if not, I would replace it completely with something modern.

If for example its a CNC machine, then modern servo systems or stepper systems would do a far better, cheaper and more reliable job!!!!

You did not give enough details for me (or anyone else!) to be able to be more specific.....

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Guest
#6

Re: Relay-Based Multivibrator

10/07/2009 12:15 PM

I think you're working on a horizontal grinder, and the circuit controlling the traverse movement fails to swing the table, if this is the case just disconect both (left-move & right-move) solenoids from the old control and conect them to the smallest, cheapest PLC with relay outputs and program it to alternate both solenoids when the proper limit switch (connect these to 2 inputs) is activated during cycle.

If the feed valve is solenoid actuated, then generate a pulse after each stroke for it, so the table "steps" normally and the metal is not rectified over and over in the same span.

But if the feed valve is "pilot" controled by the swing valve, then leave it as is, it should work. (if it is pilot controlled, it has no solenoid).

Yahlasit

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#7
In reply to #6

Re: Relay-Based Multivibrator

10/08/2009 9:08 AM

Finally after a couple of modification the machine seems to be working, but believe me, it was a nightmare to work without documentation, pulling all those wires to make a sketch to figure out how it works.

Thanks to all that gave their input.

Guru
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#8
In reply to #7

Re: Relay-Based Multivibrator

10/08/2009 10:07 AM

What is it? I did not see anywhere where that was stated....

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Associate

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#9
In reply to #8

Re: Relay-Based Multivibrator

10/08/2009 11:48 AM

SEVA polishing machine.

Guru
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#10

Re: Relay-Based Multivibrator

10/09/2009 7:22 AM

Regards.

Siemens had been manufacturing X-Ray Plants [1970/80s] having the complete automated Exposures as short as a part of a second in KW range with hundreds of relays in control circuit & also Auto Cut-Film-Changers with sme technology.

If you can approach them ask for the circuit diagram of ''Helliophose''.

May have a luck !!!!!

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#12

Re: Relay-Based Multivibrator

11/03/2009 10:20 AM

Relays are interesting do the reverse engineering on this and come up with a schematic.

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